NetHelpDesk - Leading provider of help desk software and customer support software. Trusted by IT professionals and service desks for over 20 years.
Jira - The #1 software development tool used by agile teams. Jira Software is built for every member of your software team to plan, track, and release great software.
Elementool Issue Tracking - Issue Tracking
Redmine - Flexible project management web application
LiveAgent - LiveAgent is a fully-featured web-based live chat and help desk software. It harnesses the power of a universal inbox, real-time live chat, built-in call center, and a robust customer service portal. Start your free 1 month trial today!
Trac - Trac is a project management and bug/issue tracking system. Provides an interface to Subversion and an integrated wiki.